by Stuart RothenbergApril 6, 2010 · 9:00 AM EDT

In less than a month, we will know whether Florida Gov. Charlie Crist is absolutely committed to running for the Senate this year as a Republican.

Crist, of course, says the matter is closed — that he is in the GOP race to stay. But some observers won’t be convinced until the filing deadline passes at noon on April 30.

They note the governor has launched a full-scale attack on former state Speaker Marco Rubio (R), and they speculate that he will wait to see what kind of damage he inflicts on Rubio over the next few weeks before deciding on his political course of action — whether it is dropping his Senate bid completely or running as an Independent.

There is plenty of reason for Crist to consider an Independent bid for Senate. Polling shows the governor’s standing has plummeted, and he now trails Rubio in every Republican primary poll, sometimes by breathtakingly large margins.

Crist’s base in the GOP is virtually nonexistent, according to one Florida veteran campaign watcher I spoke with recently. Since much of the governor’s job approval over the past year has come from Florida Democrats, an Independent bid aimed at weaving together a coalition of moderate Republicans, Democrats and independents doesn’t seem impossible, at least at first blush.

But savvy observers cite a number of reasons why they are skeptical that Crist will switch from the GOP contest to mount an Independent bid in the fall.

First, one insider said, Crist doesn’t yet believe that he will lose the Republican race.

“Charlie still doesn’t think he’s in trouble. He thinks this is just a phase in the race, and he and his people believe that with the stuff they have [on Rubio], they can turn it around.”

Though everyone acknowledges that the GOP primary is still almost five months away and that Crist has resources and ammunition to use against Rubio, Crist and his loyal supporters seem to be the only ones who believe that a comeback is realistic.

Veteran state observers note the trendlines of a long list of polls favor Rubio, and they comment that “nothing that Crist is throwing at Rubio is sticking,” an ominous sign for the governor.

A new controversy involving the state GOP’s former chairman, Jim Greer, who is seen by all as close to Crist, will only make it even more difficult for the governor. And the final month of the legislative session is likely to add to Crist’s woes.

Florida observers are already predicting that Rubio will receive a flood of cash after the Legislature ends its session on May 1, which will boost his campaign against Crist. Before the primary campaign began in earnest, insiders doubted that Rubio would have the resources he needed to defeat Crist. However, that concern has all but been erased.

Second, it isn’t clear that Crist could win a three-way race against Rubio as the GOP nominee and Rep. Kendrick Meek as the Democratic nominee.

In four public polls conducted over the past two months — two of them by or for Democrats, Daily Kos/Research 2000 and Public Policy Polling, and two by Republican or Republican-leaning pollsters, Fabrizio, McLaughlin & Associates and Rasmussen Reports — Rubio leads three-way contests. Three of the surveys show Crist in second place, while one has him third.

Insiders seem to agree that a Crist Independent bid would damage the governor’s credibility and rob him of much of the Republican and Democratic support he currently has in hypothetical ballot tests, certainly putting him at great risk of a third-place finish.

Running as an Independent would confirm the line of attack that Crist’s critics have leveled at him — that he is an opportunist who will do or say anything that he needs to in order to further his personal goals. And that would peel Republican and Democratic supporters away from him quickly.

Some observers doubt Crist’s fundraising ability as an Independent, noting that many of his contributors have already maxed out for the primary and general election.

Yes, Crist’s chances of winning a three-way race might be marginally better than his chances of defeating Rubio in a GOP primary, but the risk of embarrassment would also be much greater for the governor.

Rubio has become the odds-on favorite to be the state’s next Senator, though some think his road would be easier in a three-way general election contest, since a late August primary would be costly and Rubio would enter the battle against Meek weakened by Crist’s attacks. Others think a three-way race is Meek’s best chance for an upset, since the Republican vote would be divided.

But it is difficult to imagine Meek winning in November. While he will talk often about his years in the Florida Highway Patrol, his record is relatively liberal, Democrats have lost ground in the state’s generic ballot test and the recently enacted health care bill has received a very chilly reception in the state, including among seniors.

Meek is personally appealing, but he carries too much political baggage and was handed the Democratic nomination without a fight largely because Crist looked invincible when the race was taking shape.

Meek has a talented team, but the political landscape this cycle favors Republicans strongly, both nationally and in Florida. And that is likely to be decisive in November.